I don't suppose this callout is available yet in pmdg planes is it? 

 

I didn't even know about that one. In any event, this would be better off sent in via support ticket to make sure somebody from PMDG actually sees it.

Honestly, I don't think the TCAS should be taken too seriously in the Simulator, at least when flying offline.. 

First the other aircraft doesn't have a TCAS, secondly, I wouldn't trust an RA that sends me into the ground.. Just a few hours ago I was on approach into Berlin Tegel, EDDT, on RW 26R and on 26L another 737 was approaching a little higher than me.. Something that would never happen in reality btw, at least not without the other airplane being adviced to go around. But instead my TCAS threw out an RA "decend, decend now.."  at 1500' AGL... 

 

However I have no idea how the TCAS works on Vatsim or IVAO..

8 minutes ago, Ephedrin said:

However I have no idea how the TCAS works on Vatsim or IVAO..

It works, that much I can tell you. How, I have no idea, as I was flying an F-16 with no TCAS, whilst a classmate was flying the PMDG Boeing 737-800. He told me my circling around him was making his TCAS go off.

Yeah it's not perfect in the sim. On another note,  maybe it's just me but it seems "level off" callout along with showing a green line on the VSI above/below 0 would lead to more confusion? Maybe an increase/decrease climb/descent would have been better. I guess I can see where "adjust vertical speed" without aurally announcing which direction to adjust to may lead to the misunderstanding of the RA even though it gives you visual cues. But the experts have spoken. 

Do you mean the "monitor vertical speed" RA call? This will often happen when your current altitude/vertical speed will keep you clear.